The rhabdoid tumor is an exceedingly rare renal tumor that occurs predominantly in infants and young children. The tumor is highly aggressive and has a poor prognosis (Weeks et al, 1989, 1991). The histogenesis is unknown. Rhabdoid tumors have now been reported in all age groups and in sites other than the kidney (Parham et al, 1994; Fanburg-Smith et al, 1998; Ogino et al, 2000).

In tissue sections, the tumor is composed of a single population of cells that may vary in size and configuration from round or oval to spindly. The characteristic feature of these tumors is the presence of large, eosinophilic cytoplasmic inclusions that displace the nucleus of the cell to the periphery. On electron microscopy, the inclusions are composed of intermediate filaments. There is no evidence that the cytoplasmic inclusions represent an accumulation of myoglobin, but it is the appearance that gave the tumor its name. Similar cytoplasmic inclusions that stain with an antibody to myoglobin may be observed in cells of rhabdomyosarcoma. From time to time, similar cytoplasmic inclusions may be observed in other tumors, including undifferentiated large-cell lung cancer. To our knowledge, there is only one published description of the cytologic findings in FNA biopsies of rhabdoid renal tumors. In three patients, Akhtar (1991) observed large polygonal cells with abundant dense pink cytoplasm, large intracytoplasmic eosinophilic inclusions, and large nuclei with macronucleoli. “Koss’ Diagnostic Cytology and Its Histopathologic Bases, 5th Edition”

The cells show plumpy hyperchromatic nuclei with moderate pleomorphism some intranuclear pseudoinclusions are also noted.

Nerve sheath differentiation in the form of elongated, slender wavy nuclei.

Scanty cytoplasm.

On Histopathology the case was diagnosed as Malignant Peripheral Nerve Sheath Tumor.

The morphological features of MPNST are very variable. The 2 most common patterns are the spindle cell and epithelioid cell patterns. Cases showing fibromyxoid like morphology and Hemangiopericytoma like features are reported.

“The majority of MPNST are diagnosed as spindle cell sarcoma or pleomorphic sarcoma with FNA. The cellular features may suggest MPNST but a diagnosis may be difficult, even with the help of adjunctive methods. IC may be of diagnostic help if S-100 protein is positive. The positivity in MPNST is typically focal, extensive staining favours a cellular schwannoma. negative staining with desmin, SMA and muscle-specific actin excludes smooth muscle tumours and negative staining with cytokeratin, EMA and CD99 excludes synovial sarcoma”. The Cytology of Soft Tissue Tumours Dr. Mi1ns Akerman Dr. I-Ienryk A. Domanski

Helpful features include sharp radiating pain in FNA aspiration, Relation with major nerve trunk and history of Neurofibromatosis type 1 .

Langerhans cell histiocytosis is primarily a disease of childhood, although it clearly also occurs in adults, including the elderly. Classically, it is divided into three types: (i) Letterer-Siwe disease, which is prone to occur early in life and marked by multifocal skin and/or systemic involvement; (ii) Hand-Schüller-Christian disease, in which skin lesions can be accompanied by diabetes insipidus, exophthalmos, and bony defects; and (iii) unifocal disease, or eosinophilic granuloma, which affects older children and adults and in which skin involvement can accompany lesions of bones and other organs. Variant forms include an eruptive type limited to the skin that occurs in both infants and adults , a pulmonary form in young adults related to cigarette smoking , a form localized to the genitalia of elderly adults , and a rare multifocal type with marked cytologic atypia, termed Langerhans cell sarcoma . Another form presents at birth or shortly thereafter as single or multiple cutaneous papules and nodules that develop rapidly, ulcerate, and involute spontaneously; this variant is termed congenital self-healing reticulohistiocytosis . The appearance of lesions can range from crusted hemorrhagic papules in a seborrheic distribution (seen most often in Letterer-Siwe and Hand-Schüller-Christian types) to ulcerated plaques, papules, and nodules. Disease associations can include acute lymphoblastic leukemia, neonatal infection, lymphoma, and virus-associated hemophagocytic syndrome. Prognosis largely depends on the number of organ systems involved, with the poorest survivals being associated with multisystem disease.

Biopsy specimens show aggregates of cells with eosinophilic cytoplasm and nuclei displaying grooves and folds, sometimes producing a reniform appearance . These cells have a distinct tendency to infiltrate the overlying epidermis. In Langerhans cell sarcoma, cells are larger and possess nuclei with abnormal chromatin, prominent nucleoli, and frequent mitotic figures. Extravasated erythrocytes and inflammatory cells, including eosinophils, are frequently identified. The cells have the immunophenotype of Langerhans cells, expressing S-100 protein, CD1a, vimentin, and HLA-DR, and they also stain with peanut agglutinin. However, unlike normal intraepidermal Langerhans cells, the neoplastic cells express CD4 and placental alkaline phosphatase and show a different adhesion molecule expression profile. With electron microscopic analysis, Birbeck granules can be identified in a variable percentage of tumor cells. Morphologically, Langerhans cell histiocytosis can usually be distinguished from potential mimics such as xanthoma disseminatum and cutaneous T-cell lymphoma, and the immunohistochemical profile of its constituent cells is decisive. ( Sternberg’s 5th ed)

Benign melanocytic nevi in certain anatomical sites may show unusual histopathological features, Conjunctival nevi are another example of nevi at special sites that may present with worrisome features. it is safe to ‘downgrade’ the atypia that is often seen in conjunctival nevi. The lesion is often accompanied with cystic inclusions of epithelium.

Arteriovenous malformations (AVMs) are type of vascular malformation most relevant to the surgical pathologist. Because their vessels tend to leak and induce gliosis. AVMs can present with seizure disorder and also cause spontaneous hemorrhage. Best seen by trichrome or elastic stains, AVMs manifest artery-vein connections with associated arterialization of veins. Arterialization is thickening of a venous wall to the point where it resembles an artery, possibly due to fibrotic reaction to shunted arterial blood. Arteries show irregular duplication or loss of elastin . Thrombi are common. (Sternberg’s 5th ed)

Adenomatoid tumors are composed of two major elements the epithelial component and the fibrous stroma. the epithelial component is arranged in tubules, cords and nests withe cells that are flat, cuboidal to low columnar with round or oval nuclei and abundant dense cytoplasm however the cells might contain cytoplasmic vacuols and sometimes it’s so extensive that it results in signet ring like morphology as in the case of this gentle man how presents with painless small 2 cm mass in the epididymis. one should not confuse this with metastasizing signet ring carcinoma as adenomatoid tumors are very common only second to cord lipomas in such locations. Negative CEA immunostain will rule out adenocarcinoma.